1. Field of the invention.
The present invention relates to fluorinated polymers or copolymers in the form of formed articles having improved mechanical and surface properties. The polymers according to the invention contain a reinforcing filler based on glass, asbestos, silicates in general, carbon, aromatic polyamides, in the form of powders or fibres.
Said reinforcing fillers are pretreated with fluoropolyethers having functional end groups, which impart improved mechanical properties and improved surface characteristics as compared with the reinforcing fillers known in the art.
The fillers treated according to the present invention remain perfectly dispersed in the polymer, whereby preventing, during the mechanical treatments, the separation thereof in heterogeneous areas which would impair the mechanical and surface properties.
2. The Prior art.
As is well known, in order to improve the mechanical and surface characteristics of the fluorinated polymers, these are reinforced with fillers, in particular glass fibres treated with organic compounds with a view to increasing the compatibility of such fibres with polymers such as, for example, polytetrafluoroethylene.
According to U.S. Pat. No. 3,787,281, the glass fibre treatment is carried out by means of a hydrolizable nonfluorinated siloxane compound containing an aminic end group.
According to GB Pat. No. 1,250,798, both siloxane compounds and alkoxy-titanium compounds are utilized for the surface treatment of reinforcing materials such as glass fibres or metal powders. The compounds utilized for said treatment do not contain fluorine; examples thereof are in particular Ti-tetrabutylate, 3-aminopropyl-triethoxy-silane and phenylmethyl-polysiloxane.
The articles obtained from the polymers which have been reinforced according to the conventional methods are not always satisfactory as regards a perfect homogenization of the reinforcing material with the polymer; such non-homogeneity results in an irregular surface appearance and in a grey shade as well as in a rather low mechanical strength, in particular as concerns the flex-life on treated fabrics.